Very little is known about Neanderthal cultures, particularly early ones. Other than lithic implements and exceptional bone tools, very few artefacts have been preserved. While those that do remain ...include red and black pigments and burial sites, these indications of modernity are extremely sparse and few have been precisely dated, thus greatly limiting our knowledge of these predecessors of modern humans. Here we report the dating of annular constructions made of broken stalagmites found deep in Bruniquel Cave in southwest France. The regular geometry of the stalagmite circles, the arrangement of broken stalagmites and several traces of fire demonstrate the anthropogenic origin of these constructions. Uranium-series dating of stalagmite regrowths on the structures and on burnt bone, combined with the dating of stalagmite tips in the structures, give a reliable and replicated age of 176.5 thousand years (±2.1 thousand years), making these edifices among the oldest known well-dated constructions made by humans. Their presence at 336 metres from the entrance of the cave indicates that humans from this period had already mastered the underground environment, which can be considered a major step in human modernity.
Accurate reconstruction of past ocean temperatures is of critical importance to paleoclimatology. Carbonate clumped isotope thermometry (“Δ47”) is a relatively recent technique based on the strong ...relationship between calcification temperature and the statistical excess of 13C–18O bonds in carbonates. Its application to foraminifera holds great scientific potential, particularly because Δ47 paleotemperature reconstructions do not require assumptions regarding the 18O composition of seawater. However there are still relatively few published observations investigating the potential influence of parameters such as salinity or foraminiferal size and species. We present a new calibration data set based on 234 replicate analyses of 9 planktonic and 2 benthic species of foraminifera collected from recent core-top sediments, with calcification temperatures ranging from −2 to 25 °C. We observe a strong relationship between Δ47 values and independent, oxygen-18 estimates of calcification temperatures:Δ47 = 41.63 × 103/T2 + 0.2056
The formal precision of this regression (± 0.7–1.0 °C at 95 % confidence level) is much smaller than typical analytical errors. Our observations confirm the absence of significant species-specific biases or salinity effects. We also investigate potential foraminifer size effects between 200 and >560 μm in 6 species, and conclude that all size fractions from a given core-top location and species display statistically undistinguishable Δ47 values. These findings provide a robust foundation for future inter-laboratories comparisons and paleoceanographic applications.
Increasing atmospheric CO
from man-made climate change is reducing surface ocean pH. Due to limited instrumental measurements and historical pH records in the world's oceans, seawater pH variability ...at the decadal and centennial scale remains largely unknown and requires documentation. Here we present evidence of striking secular trends of decreasing pH since the late nineteenth century with pronounced interannual to decadal-interdecadal pH variability in the South Pacific Ocean from 1689 to 2011 CE. High-amplitude oceanic pH changes, likely related to atmospheric CO
uptake and seawater dissolved inorganic carbon fluctuations, reveal a coupled relationship to sea surface temperature variations and highlight the marked influence of El Niño/Southern Oscillation and Interdecadal Pacific Oscillation. We suggest changing surface winds strength and zonal advection processes as the main drivers responsible for regional pH variability up to 1881 CE, followed by the prominent role of anthropogenic CO
in accelerating the process of ocean acidification.
U‐Th ages and temperatures derived from Li/Mg have been measured on coral fragments of Lophelia pertusa and Madrepora oculata collected from two sediment cores, which were taken from cold‐water coral ...(CWC) mounds at 700–790m water depth at the SW Rockall Trough margin. Our data, combined with previous published data, have allowed us to first estimate the occurrence of CWC at the SW Rockall Trough margin during the Holocene and, second, to better constrain the environmental conditions driving variability in CWC growth. CWC abundance is marked by a pronounced increase in the mid‐Holocene (∼6 ka) and is modulated by millennial‐scale variability throughout the late‐Holocene. The mid‐Holocene proliferation of CWC coincides with lowest IRD abundances and a major reorganization of the circulation at thermocline depth in the Rockall Trough, marked by the progressive replacement of the fresh‐cold Sub‐Arctic Intermediate Water (SAIW) by the saltier and nutrient‐rich Eastern North Atlantic Water (ENAW). This event must have established a modern‐like winter mixed layer and thermocline structure, generating suitable conditions for enhanced surface productivity, downslope transport of food particles, bottom current acceleration at mound depth and thus CWC growth. Several short time intervals of decreased CWC occurrences closely match prominent increases in North Atlantic drift ice and storminess in Northern Europe. We, therefore, propose that high detrital supply and/or changes in the vertical density gradient associated with millennial‐scale ice‐rafted detritus (IRD) events are the likely controlling factors for CWC growth and subsequent mound formation on the SW Rockall Trough margin.
Key Points
First detailed record of cold‐water corals occurrence at the SW Rockall Trough margin during the Holocene
Evidence of a mid‐Holocene increase in the cold‐water corals occurrence associated to major reorganization of the hydrology
Strong evidence of millennial climatic control on the CWC growth in the SW Rockall Trough during the late‐Holocene
Introduction:
Characterizing the thermal habitat of fish is key to understanding their ecological requirements in order to make appropriate management plans for the preservation of fish populations ...in the context of climate change. Little is known about the thermal habitat of the early life stages of fish (larvae and juveniles), as most methods have been designed for large, easily handled individuals. In particular, the study of otoliths holds great promise for unveiling the early thermal history of fish, although it is challenging to implement due to the very small size of the biological material.
Methods:
The stable oxygen isotope content (
δ
18
O
) of biogenic carbonates (such as otoliths) can be used to reconstruct the life temperature of fish individuals. However, relationships between
δ
18
O
of otoliths and ambient temperature are scarce and mainly developed for commercial species. In this study, we assessed the
δ
18
O
of juvenile European chub (
Squalius cephalus
, Linnaeus 1758) living in a section of the lower Rhône River in France.
Results:
The
δ
18
O
of otoliths showed significant relationship with ambient temperature
δ
18
O
oto(VPDB)
- δ
18
O
w(VPDB)
= 33.391 – 0.2641 * T (°C), and the relationship between temperature and the fractionation factor (α) was 1,000 ln
α
= −43.472 + 21.205 1,000/T(K).
Discussion:
As expected, back-calculated temperatures from these equations were in much better agreement with the measured
in situ
temperatures than previously published equations. This equation is the first to be developed for leuciscid fish in Europe and the second in the world.
We present ion microprobe measurements of oxygen isotopic compositions in the deep-sea coral
Lophelia pertusa. Compared to bulk skeletal aragonite fibres, the EMZ (early mineralization zone), near ...the inside of the calyx, was systematically depleted in
18O. Rayleigh fractionation from a semi-closed fluid reservoir does not explain this and other geochemical differences. Furthermore, pH values estimated from skeletal δ
11B data are inconsistent with the idea that EMZ (or centres of calcification)
18O depletion reflects a more alkaline calcification environment. Our data, combined with microstructural and geochemical observations, indicate that the aragonitic fibres and EMZ are formed by a compartmentalized mineralization calicoblastic ectoderm, which exerts strong biological control on the composition of the skeleton. Hence, we propose a new model whereby amorphous calcium carbonates (ACC) are precursors to the EMZ, whereas the fibre precipitation is probably governed by kinetic processes.
Quantifying the scale and importance of individual dispersion between populations and life stages is a key challenge in marine ecology. The common sole (Solea solea), an important commercial flatfish ...in the North Sea, Atlantic Ocean and the Mediterranean Sea, has a marine pelagic larval stage, a benthic juvenile stage in coastal nurseries (lagoons, estuaries or shallow marine areas) and a benthic adult stage in deeper marine waters on the continental shelf. To date, the ecological connectivity among these life stages has been little assessed in the Mediterranean. Here, such an assessment is provided for the first time for the Gulf of Lions, NW Mediterranean, based on a dataset on otolith microchemistry and stable isotopic composition as indicators of the water masses inhabited by individual fish. Specifically, otolith Ba/Ca and Sr/Ca profiles, and δ(13)C and δ(18)O values of adults collected in four areas of the Gulf of Lions were compared with those of young-of-the-year collected in different coastal nurseries. Results showed that a high proportion of adults (>46%) were influenced by river inputs during their larval stage. Furthermore Sr/Ca ratios and the otolith length at one year of age revealed that most adults (∼70%) spent their juvenile stage in nurseries with high salinity, whereas the remainder used brackish environments. In total, data were consistent with the use of six nursery types, three with high salinity (marine areas and two types of highly saline lagoons) and three brackish (coastal areas near river mouths, and two types of brackish environments), all of which contributed to the replenishment of adult populations. These finding implicated panmixia in sole population in the Gulf of Lions and claimed for a habitat integrated management of fisheries.
The lithium isotope compositions (
7Li/
6Li) and Li/Ca ratios of shallow-water and deep-sea corals (
Porites lutea,
Cladocora caespitosa,
Lophelia pertusa and
Desmophyllum cristagalli) were measured ...using a Caméca ims 1270 ion microprobe. The two
C. caespitosa samples were grown under controlled conditions at CO
2 partial pressures (pCO
2) of 416
±
29
µatm and 729
±
30
µatm, respectively.
In situ analyses show that all samples are isotopically homogeneous (within analytical precision, ±
1.1‰, 1
σ) and display significantly lower
δ
7Li values relative to seawater, indicating a significant isotope fractionation during aragonite formation. In contrast to all other elements analysed so far, there is no relationship between the Li isotopic compositions and the skeletal ultrastructure. However, Li/Ca does show variation correlated with ultrastructure, albeit with significant differences between species. This implies that the biomineralization mechanisms, which are supposed to be different for the different skeletal components, do not influence the Li isotopic composition in corals. In particular, the model of Rayleigh fractionation in a semi-enclosed calcifying fluid is incompatible with the homogeneity of the Li isotope compositions at the micrometer scale. We also show that changes in pCO
2 (and pH) do not significantly affect the Li isotope signature. Nevertheless, a small but significant and systematic difference in Li isotopic composition is observed between deep-sea azooxanthellate and shallow-water zooxanthellate corals. The lack of dependence on pH and pCO
2 and on skeletal ultrastructure indicates that the Li isotopic signature of corals could be used as a proxy for reconstructing the paleo-
δ
7Li of seawater and, potentially, for deconvolving past continental weathering rates.
Coral skeletons are built by Ca-carbonate (calcite or aragonite) crystals that exhibit distinct morphological patterns and specific spatial arrangements that constitute skeletal microstructures. ...Additionally, the long-standing recognition that distinct coral species growing in similar conditions are able to record environmental changes with species-specific responses provides convincing evidence that, beyond the thermodynamic rules for chemical precipitation, a biological influence is at work during the crystallization process. Through several series of comparative structural and geochemical (elemental and isotopic) data, this paper aims to firmly establish the specific properties of the distinct major taxonomic units that are commonly gathered as deep-water “corals” in current literature. Moreover, taking advantage of recent micrometric and infra-micrometric observations, attention is drawn to the remarkable similarity of the calcareous material observed at the nanoscale. These observations suggest a common biomineralization model in which mineralogical criteria are not the leading factors for the interpretation of the geochemical measurements.
X‐ray fluorescence, grain‐size and oxygen and carbon stable isotope measurements of a 33 m long piston core, recovered from the Pen Duick drift located at the foot of the prominent Pen Duick ...Escarpment (Atlantic Moroccan margin), are combined to decipher past oceanographic conditions. The data indicate that, similar to the northern Gulf of Cádiz, the Azores Front exerts a major control on the palaeoclimatology of the region. Contrasting the northern Gulf of Cádiz, where Mediterranean Outflow Water is the main water mass at similar water depths, the palaeoceanography of the studied area is mostly influenced by the amount of Antarctic Intermediate Water advected from the south. The density contrast between the Antarctic Intermediate Water and the overlying North Atlantic Central Water determined the strength of the prevailing internal tides and corresponding high current speeds, which drastically impacted the sedimentary record. The most notable impact is the presence of a 7.8 kyr condensed section (30.5–22.7 ka bp). The formation of the Pen Duick sediment drift was not just controlled by the strength of the bottom currents and the intensity of the internal tides, but also by the amount of (aeolian) sediment supplied to the region. Although variable, drift‐growth phases seem to mainly occur during colder periods of the last glacial, that is Heinrich and Dansgaard‐Oeschger events during Marine Isotope Stage 3 and late Marine Isotope Stage 2. These periods, characterised by increased aeolian dust supply and higher bottom currents, coincide with a phase of prolific cold‐water coral growth and enhanced coral mound formation as recorded in numerous cores obtained from the southern Gulf of Cádiz. This implies that both records (on and off mound cores) are pivotal to provide the complete picture of the palaeoclimatic and palaeoceanographic conditions in the region.
This paper covers the palaeoceanography and hydrodynamic variability of the southern Gulf of Cádiz, based on the study of an 18 m long sediment core from the region. The sediment core is analysed and compared to surrounding cores and studies in order to decipher the climatic and oceanographic evolution during the last 47 kyrs. The study yields insights into the changing importance of the Azores Front in the region as well as the varying sources of sediment supply to the prevailing sediment drift.
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